Process for separating gases

ABSTRACT

A process for removing a gaseous constituent from a gaseous mixture involving contacting a layer of electrolyte with the gaseous mixture and then electrolytically decomposing the gaseous constituent into its component parts.

United States Patent Russell et al. 51 Apr. 11, 1972 [54] PROCESS FOR SEPARATING GASES 1,543,357 6/1925 Baur ..204/60 X [72] Inventors: Cornelius R Rum, west Hartford; Sid 2,829,092 4/1958 Andneux etal. ..204/60 Russell s i both of Co Taylor 3,173,849 3/1965 Shearer et al ..204/60 [73] Assignee: United Aircraft Corporation, East Hartford Conn Primary Examiner-John H. Mack [22] Filed; N v.- 18, 1970 Assistant Examiner-D. R. Valentine 1 pp No: 90,527 Attorney-Owen J. Meegan ABSTRACT [52] U.S. Cl ..204/60, 204/212, 204/246,

204/247 A proces s for removing a gaseous constltuent from a gaseous [51] lnt.Cl ..B0lk l/00 mlxture mvolvmg comaamg a layer electrolyte the 58 Field ofSearch ..204/60,2l2 gaseous mixture and then elestrolytically decomposing the gaseous constituent into its component parts. [56] References Cited 8 Cl i 2 Drawing Figures UNITED STATES PATENTS 1,301,832 4/1919 Gerber ..204/2l2 ponent from a gaseous mixture. Carbon dioxide, often becomes admixed with air as a result Usually there is no need'to separate-the carbon the air because its quantity is small, relative to the total quantilJField of the Invention 'The present invention relates to electrochemical processes and particularly to ones in which decomposable gases are absorbedin an electrolyte and subsequently decomposed. More specifically,the present invention relatesto the absorption of carbon dioxideadmixed in air on a thin film of a fused electrolyte and the subsequent decomposition into carbon and oxygen.

' It isfrequently very desirable to separate one gaseous comfor example, of breathing. dioxide from ty of air in the atmosphere. When the admixture occurs in a closed system, however, techniques for separating the gases and recycling oxygen frequently become necessary. The

separation, electrolysis and recycling becomes even more difficult when a closed system is operated without gravity. Controlling solids and liquids is difficult under'these conditions.

25 Description of the Prior Art As has been mentioned in the U.S. Pat. to Russell et al, No. 3,463,209, certain alkali metals, particularly lithium, electrochemically reduced at the cathode in an-electrolyte containing lithium carbonate, react chemically with carbon dioxide in solution to deposit carbon'as an adherent layer on the surface of the cathode, to the electrolyte. When this concept is used with relatively thin adherent films of a fused electrolyte, then the system can be operated where there is no gravity.

In the overall process, three main steps occur:

I. Cathode reaction: CO 4e C 30"" 2. Anode reaction: 2 O" O, 4e

-'3.- Scrubbing reaction: CO +O CO Stated as an overallreactionz CO C SUMMARY OF THE INVENTION ln accordance with the present invention, a continuously recycling-layer of fused electrolyte is exposed to a gaseous mixture. ofa carrier, such as air, and'carbon dioxide. The film isFfirst movedto anabsorbing position where it contacts the gaseous mixture and: reacts with the carbon dioxide'to form a carbonate. From the absorbing position, the film is then moved'tma cathodicposition where the carbonate is broken downinto carbon and oxygen ions. The carbon deposits as an adherent coating on the cathode. The electrolyte now enrichedinoxygen ionsis then moved-to the anodic position,

cylindrical scrubber drum. Carbon dioxide-ladenair contacts the drum-and'the CO- is absorbedinto the electrolyte: The drumrevolves so that theCO enriched electrolytereaches thecathodicposition wherethecarbondioxide is decomposed 'into carbon and oxygen ions. The carbon deposits as a solid on thercathode. As therdrum rotatesfurther, the oxygen ions are carried {along in the electrolyte to the anodic position where two-thirds of them are discharged to form oxygen gas. The oxygen gas is added to and reconstitutes the air wlu'ch has been scrubbed of CO As the drum continues its rotation, the electrolyte with remaining one-third of the oxygen ions returns to the absorbing position for re-contact with carbon dioxideladen air and the process repeats.

Theanode and the cathode are preferably two revolving drums, however, stationary. electrodes can also be used. Moreover, some constructions maybe used which include a stationary anode and a drum-type cathode or visa versa. The entire cylindrical drum upon which the electrolyte is disposed returning lithium ions and oxide ions' is heated to a temperature sufficient to maintain the electrolyte in a molten state.

BRIEF DESCRIPTION OF THE DRAWINGS stationary.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an axle 2 is centrally disposed within scrubbing drum 1 and is mounted upon slotted holes (not shown) in a housing so that it can revolve freely. The scrubber drum 1 is formed of a tube 5 of a porous refractory ceramic material, such as magnesium oxide with metal end plugs 3 and 15 charged with a reservoir of electrolyte (not shown).

An anode 6 is formed of an electrically conductive cylindrical shell 7 mounted upon a hub 8 with mile 9 centrally disposed therein. A cathode 10 is similar in construction to anode 6 and includes conductive shell 11 mounted upon hub 12 with centrally disposed axle 14. Theaxles of both the anode 6 and cathode 10 are mounted in slotted holes so that they can rotate freely.

The anode 6 and cathode 10 are connected to opposite sides of a power supply 15 through wiper arms 16 and 17 respectively which contact the surface of the shells. Other suitable element contacts which accomplish the electrolysis can be used also, for example the axles can be connected to the power supply with interconnections to the respective drum surfaces.

The mounting of the cathode 10 is accomplished by placing its axle in holes which will accommodate the gradual buildup of carbon. These holes can be slotted to allow relative outward movement of the cathode from the scrubber while permitting them to bear against each other. Since the rollers are free to move relative to' each other, the amount of pressure they exert upon each other is constant.

Movement of the rollers during operation can be accomplished through conventional gearing, (now shown). One or two drums can be driven and the rest can follow or all three can be driven, as desired and depending upon the size of the drums. To provide electrical contact for the anode and cathode, brushes can be fabricated of a suitable metal, arranged to bear upon the surfaces. A positive spring force is preferred, especially one which exerts pressure at the operating temperature of the device-In order to seal the equipment and make all gases flow through the equipment, a pair of spring wiper blades 19 and 21 are provided which brush against the scrubber drum 1.

When operating the equipment, the temperature of the scrubber drum 1 was raised to between 950 and 1,350 F. preferably l,100 F. The electrolyte became molten and wet the external surfaces of all three drums. A'one-half of one percent by volume mixture of CO -in'air was introduced into the scrubber'throughinlet port 18 at a temperature near about 1,100 E, and a flow rate of 0.0058 lb/minute. The gas flowed through housing l 9'and contacted a thin layer 20 of fused electrolyte, 60 Wt% LiCl, 36 Wt% Li CO,, 4 Wt% Li O. The CO was scrubbed from thega'seousmixture. A constant current of 3 amperes was applied at 2 to 5 volts to the anode and cathode and carbon was plated upon the cathode 10. Oxygen was produced at the anode 6 and removed from the system with the purified air through port 22.

Referring to FIG. 2 another embodiment is shown. The scrubber drurn 30 is the same as that describedin FIG. 1. In place of counter-rotating anodes and cathodes, however, a pair of spring biased wiper arms or conductors are used. An electrical circuit is made between the layer of fused electrolyte 31 and cathode 32 and anode 33. Gas, laden with C0,, passes into port 34 where it contacts layer 31 and the CO is absorbed. The layer 31 is rotated on the drum to the anodic position where it contacts anode 33 and oxygen is released. The oxygen mingles with the incoming air and eventually leaves through port 35. Scrubbing drum 30 revolves from the anodic position to contact the cathode 32 and carbon is plated out thereupon. A potential is established between the anode 33 and cathode 32 by a power supply 36. To compensate for the gradually increasing thickness of carbon on cathode 32, the latter is slowly withdrawn through support 37 by an appropriate indexing device (not shown).

It is apparent that modifications and changes can be made within the spirit and scope of the present invention. It is our intention, however, only to be limited by the scope of the appended claims.

As our invention we claim:

1. In the process of purifying gases, the steps which comprise: flowing a gaseous mixture over a fused layer of absorbent electrolyte whereby at least one of the components of the gaseous mixture will be absorbed therein; moving said layer of electrolyte containing said absorbed gas to a first position while applying one polarity of a potential thereto, whereby the component is decomposed into charged elements, the elements of one charge being attracted to said one polarity of said potential and removed from said electrolyte; subsequently moving the layer of electrolyte to a second position while applying the opposite polarity of said potential thereto whereby oppositely charged elements are attracted to the opposed polarities of said potential and removed from the electrolyte; recycling said electrolyte into contact with said gaseous mixture whereby it will again absorb components of the gaseous mixture.

2. The process according to claim 1 wherein the electrolyte is heated to a temperature of between about 950 and 1,350 F.

3. The process according to claim 1 wherein the gaseous mixture contains carbon dioxide, said carbon dioxide being absorbed by the molten electrolyte and then being decomposed into carbon and oxygen ions at the first position, the oxygen ions then being oxidized to oxygen gas at the second position, the oxygen gas then evolving from the electrolyte and readmixing with the gaseous mixture for recycle.

4. The process according to claim 3 wherein at the first position the electrolyte contacts an anode and oxygen evolves at that point and at the second position the electrolyte contacts a cathode and carbon firmly attaches itself thereupon.

5. The process according to claim 1 wherein the layer of electrolyte is disposed upon a non-conductive cylindrical roller and the one polarity of the potential applied at the first position is implied through a second roller contacting said electrolyte and the opposite polarity of the potential implied at said second position is implied through a third roller contacting said electrolyte.

6. The process according to claim 4 wherein said first roller is an anode and carbon dioxide is absorbed into the electrolyte and oxygen evolves at that point and said second roller is a cathode and carbon deposits thereupon.

7. The process according to claim 1 wherein the layer of electrolyte is disposed upon a non-conductive cylindrical roller and the one polarity of the potential applied at the first position is imposed through an electrode contacting said electrolyte and the opposite polarity of the potential applied at the second position is applied through an electrode contacting said electrolyte.

8. The process according to claim 7 wherein said first electrode is an anode and carbon dioxide absorbed into the electrolyte and oxygen evolves at that point and the second electrode is a cathode and carbon deposits thereupon.

UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION Patent no. 'r 5 7 Dated April 11, 1972 t -(g Cornelius R. Russell, Sid Russell It is certifiedthat error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

.Add the following paragraph to the specification:

The invention described herein was made in the performance of work under a NASA contract and is subject to the provisions of Section305 of the National Aeronautics and Space Act of 1958, Public Law 85-568 (72. Stat. 435; 42 U.S-.C. 2457) Signed and sealed this 5th day of December 1972.

E L) 'Attest:

. EDWARD M.'FLE'IC HER JR a 5 ROBERT GOTTS CHALK Att est'ing Officer I Commissioner of Patents 

2. The process according to claim 1 wherein the electrolyte is heated to a temperature of between about 950* and 1,350* F.
 3. The process according to claim 1 wherein the gaseous mixture contains carbon dioxide, said carbon dioxide being absorbed by the molten electrolyte and then being decomposed into carbon and oxygen ions at the first position, the oxygen ions then being oxidized to oxygen gas at the second position, the oxygen gas then evolving from the electrolyte and readmixing with the gaseous mixture for recycle.
 4. The process according to claim 3 wherein at the first position the electrolyte contacts an anode and oxygen evolves at that point and at the second position the electrolyte contacts a cathode and carbon firmly attaches itself thereupon.
 5. The process according to claim 1 wherein the layer of electrolyte is disposed upon a non-conductive cylindrical roller and the one polarity of the potential applied at the first position is implied through a second roller contacting said electrolyte and the opposite polarity of the potential implied at said second position is implied through a third roller contacting said elEctrolyte.
 6. The process according to claim 4 wherein said first roller is an anode and carbon dioxide is absorbed into the electrolyte and oxygen evolves at that point and said second roller is a cathode and carbon deposits thereupon.
 7. The process according to claim 1 wherein the layer of electrolyte is disposed upon a non-conductive cylindrical roller and the one polarity of the potential applied at the first position is imposed through an electrode contacting said electrolyte and the opposite polarity of the potential applied at the second position is applied through an electrode contacting said electrolyte.
 8. The process according to claim 7 wherein said first electrode is an anode and carbon dioxide absorbed into the electrolyte and oxygen evolves at that point and the second electrode is a cathode and carbon deposits thereupon. 